Electrical contact jaw



y 1931. E. e. JOHNSON 7 ELECTRICAL CONTACT JAW I Filed Aug. 13, 1924 7 L PM jnvanior firms? 6. J0%nson 1: ,heated as. there isin the construction of 5 prior application .hereinbefore referred to, I and the grippingeffectdue to the heating the case of the present invention is material- Patented May 19, 1931 UNITED STATES ATENT OFFICE ERNEST G. JOHNSON, OF BOSTON, MASSACHUSETTS, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO THE PALMER ELECTRIC & MANUFACTURING CO., OF WALTHAIM', MAS SACHUSETTS, A CORPORATION OF MASSACHUSETTS ELECTRICAL coii'mcr .mw

Application filed August 13, 1924. Serial No. 731,777.

Switch and fuse jaws and the like have heretofore been formed up of bent sheet or bar stock, the bends being so disposed that a tendency to straighten them such as may be occasioned by the heatin effects of the current passing therethroug tends to separate the prongs or contact elements so that the switch or other blade which passes therebetween and is the mating contact member becomes less firmly gripped. This increases the contact resistance between, the-members and the consequent heating effect, which in turn tends to further separate the contacts. For this reason ithas often been found 15 necessary to spring the jaws together to such an extent when the blade is removed that it is very difiicult to insert the blade, a heavy pressure onthe blades when the parts are cold being necessary'in order that sufficient 30 tightly than when the parts are cold. In the form there disclosed heating causes both the jaws to tend to bend in the same direction relative to their supportingflbases, the contact portion of one, however, to a greater 5 extent thanthe other so that the resultant effect is to urge these contact portions closer together as they become more highly heated.

In the present invention the jaws are so.

formed that under heating efi'ects the, contact portions tend to. bend in opposite'direce .other. There is thus no tendency for the 'aws to change the angular position of the. ladeor other CODtflCtIllQIGbBtWGQh relative 1: to thesupporting base when the parts become ly greater. Of course as the gripping effort pressure to maintain the firm contact neces 'sary to properly carry the desired current tions relative to their bases and toward each becomes greater the contact resistance between the parts is decreased which acts to decrease further heating.

For a more complete understanding of this invention, reference may be had to the accompanying drawings in which Figure 1 1s a fragmentary side elevation of afuse mounting showing the clip or contact jaws at one end thereof constructed accordmg to this 1nvent1on. Flgure 2 1s an end elevatlon thereof.

Figure 3 is a side elevation of jaws pa-rticularly designed for a switch.

. Figure 4 is a similar view of a modified form of switch jaw.- I a Figure 5 illustrates a further modification of the jaw contacting elements. 4

Referring first to Figures 1 and 2, the clip or jaws for receiving the conductor blade 1 of the fuse 2 comprises a pair ofspaced bars or strips-3 and 4',1.these bars being spaced apart sufficiently to permit the conductor 1 to be gripped tightly therebetween. At their lower ends they are turned outwardly away from each other as shown at 5 and 6 to form base portions which are attached as by means of rivets 10 to a conductor barf? shown as fixed to the panel 8 as by means of the screws 9. Above, the normal position of the-conductor 1 when'placed between the barsBand 4 they may have struck inwardly therefrom projections 12 which act in addition to the pressure exerted by the resiliency of the bars against the conductor 1 to hold the conductorin position.

Any heating of the bars 3 and 4 causes the bends at 15 between their upstanding and base portions to tend to straighten, thus tending to bend their upper ends toward teach other and increasing the pressure with 'w'hich the parts 3 and een agej the conductor, thus decreasing the f contact" resistance between lthese' partfs and 'reducing the tendency fur- 'therlheating.

InFigureBa construction particularly applicable L to knife switches is shown. This comprises a piece of bar stock' having a portion intermediate itsends asat' 20fsubstantially flat, portions at: either end thereof being bent toward each other and overlying the 'upper face of the portion 20 as shown at 21. and 22. The ends of these portlons are then bent upwardly as at 23 and 24 to form upstanding spaced contact members 25 and 26. Screws as 27 threaded through the portion 20 and the portions 21 and 22 on opposite sides of the upstanding contacts 25 and 26 may be emplo -'ed to fix the jaw to a supporting panel or lock 28. As shown one end ortion of double thickness as that formed y the intermediate Egrtion 20 and the overlying portion 21 is nt upwardly as at 30 either at the corners only or entirely across the width of the material to retain the conductor wire in position beneath the head 31 of a binding screw 32 threaded through the portions 21 and 20 adjacent thereto. The intermediate portion 20 in this construction serves as a conductor joining the two contact members. Here also it will be seenthat if the jaws are heated the contacting portions 25 and 26 will tend to move toward each other as shown by dotted lines, the bends at 23 and 2 being straightened by the heating action. The bends at the ends of the intermediatepor'tion are held against unbendin by the screws 27. If a switch blade is place between these jaws preventing them from actually moving together to an appreciable extent the pressure on the switch blade is corres ondingly increased.

In igure 4 a slight modification is shown in which one of the contacts is formed double as shown the contact 25 being extended an its end bent downwardly as at 250 toward the rtion 20 and facing the contact member 26. Where this construction is employed the heating not only tends to straighten the bends at 23 and 24 but also tends to straighten the bends at40 and 41 where the end 250 is bent to extend downwardly toward the intermediate portion 20. There is thus the cumulative effect of the partially straightening of all of these bends tending to further increase the ressure exerted on the switch blade which 1s passed between the members 250-and 260. It is of course evident that if desired one of the contact elements ma be extended and bent back parallel to itse f to form a double prong for the fuse clip otherwise formed as is illustrated in Figures 1 and 2.

In place of forming only one contact element double, both may be formed double if desired as shown in Figure 5, the free ends of 'both of the contact strip being bent downwardly facing the opposite strip as shown, so that the ends 250 and 260 of the portions 25 and 26 are in opposed spaced relation in position to receive the switch blade or fuse conductor therebetween. With this form the gripping effort due to heating is still further increased since the bends 42 and 43 of the member 26 also tend to straighten thus moving the end 260 toward the end 250.

In all the constructions shown it will be noted that the base portion of the jaws is formed by initial bends of the stock from the switch blade receiving portion in directions away from each other so that any heating of the contacts extending to these initial bends tending to straighten them results in the contacts bendin toward each other. Where other bends in the stock are also made at the base of the jaw, as in the form shown in Figures 3 and 4, these bends are more remote from the heated portions so that the unbending tendency is less and such unbending is prevented from actually occurring except in inconsequential amount by the fixing of the superposed layers of stock together as by the screws 27 and 32 indicated in Figure 3.

Having thus described certain embodiments of this invention is should be evident that various changes and modifications might be made therein without departing from its spirit or scope as defined by the appended claims.

I claim:

1. Electrical contact jaws comprising a pair of electrically connected strip contact members spaced apart to receive a conductor member therebetween, each of said contact members having an integral fixed base portion at its lower end extending initially away from the other contact member, and at least one of said contact members having its free end bent downwardly and facing the other contact member to form a double prong.

2. A switch jaw comprising a piece of bar stock having a substantially flat portion intermediate its ends, the portions beyond said intermediate portion being bent toward each other to overlie said intermediate portion and being fixed thereto and then bent directly away therefrom and from each other to form a pair of contact members 5 aced to receive a conducting member there tween.

3. A switch jaw comprising a piece of bar stock having a substantially flat portion intermediate its ends, the portions beyond said intermediate portions being bent toward each other to overlie said intermediate portion and being fixed thereto and then bent directlfy away therefrom and from each other to orm a pair of contact members s aced to receive a conducting member there tween, at least one of the ends of said strip being turned back against said intermediate portion and facing the opposite end to form a double prong.

4. A switch jaw comprising a piece of bar stock having a substantially flat portion intermediate its ends, the ortions beyond said intermediate portion bemg bent toward each other to overhe said intermediate portion and being fixed thereto and form a base portion and then bent directly away therefrom and fromeach otherto form a pairofcontact members spaced to receive a conducting member therebetween, and one end of said base portion having apart bent up to form a wire retaining element. 1

5. A switch jaw comprising a piece of bar stock havin a substantially flat portion intermediate 1ts ends, the portions beyond said intermediate portion belng bent toward each other to overlie said intermediate portion and being fixed thereto and form a base portion and then bent directly away therefrom and from each other to form a pair of contact members spaced to receive a conducting member therebetween, at least one of the ends of said strip being turned back toward said intermediate portion and facing the opposite end to form a double prong, one end of said base portion having a part bent ill) to form a Y wire retaining element.

In testimony whereof I have aflixed my signature.

- ERNEST G. JOHNSON. 

